This invention relates generally to the dispensing of tablets, especially for use in the clinical analysis of biological samples. In particular, the invention relates to apparatus for dispensing tablets and to clinical analysis systems for the analysis of biological samples incorporating such apparatus. It also relates to methods of tablet dispensing and methods of clinical analysis employing tablet dispensing.
The present invention is particularly useful in automated clinical analyzers for determining the presence and levels of one or more selected constituents in relatively small biological liquid samples. Numerous automated clinical analyzers are known and widely used in hospital clinical laboratories. A preferred form of such analyzers is known as a single track clinical analyzer in which a series of cuvettes is advanced in turn past a plurality of processing stations arranged in line and the processing stations are selectively activated in varying permutations for different cuvettes.
An automated single track clinical analyzer is described in commonly owned U.S. Pat. No. 4,528,159, issued July 9, 1985 entitled "Automated Analysis Instrument System." The single track analyzer can perform different analytical profiles (i.e., profile analysis) or the same analytical test on a series of different patient samples (i.e., batch analysis). In either mode of the single track analyzer, the cuvettes containing samples are processed serially along a single track within the analyzer.
The single track analyzer is capable of performing multiple selected tests on a single specimen and is adapted for handling "stat" testing of emergency samples and routine chemistries. To this end the analyzer is adapted to dispense different permutations of reagent and liquid biological samples into successive, relatively small cuvettes advanced therethrough. The analyzer has multiple analysis stations to which the cuvettes are fed in turn so that examination of the treated samples can be effected at varying time intervals without limiting the throughput of the instrument. These multiple analysis stations permit their positioning at read times that are closely related to theoretical optimal kinetic and endpoint reaction read times.
The single track analyzer utilizes a disposable cuvette belt formed from thin plastic film and defining a series of discrete reaction compartments (cuvettes) which are transported in line through the instrument. The cuvettes are relatively small. They are generally, for example, capable of holding a final reaction volume of approximately 300 microliters. The patient sample in the cuvette is approximately 2 to 20 microliters. Such a cuvette belt is described in commonly owned U.S. patent application Ser. No. 284,842, filed July 20, 1981, entitled "Cuvette System For Automated Chemical Analyzers". Such a belt provides handling flexibility and avoids the crosscontamination associated with flow-through cuvettes as well as avoiding the washing required of reusable cuvettes.
The earlier clinical analyzers discussed above employed liquid reagent, and mixing of the reagent with the diluent prior to addition of the biological sample was achieved by pipetting a stream of the liquid reagent into the cuvette so as to produce a vortex-type mixing process. A preferred feature of the analyzer disclosed in U.S. Pat. No. 4,528,159 is that it is adapted to utilize dry particulate reagents, preferably in tablet form, which are dispensed into the cuvettes from a rotating carousel which can hold a large number of doses. A preferred embodiment of tablet dispenser is described in commonly owned U.S. Pat. No. 4,405,060 entitled "Tablet Dispensing Device".
In order to effect dissolution of the dry particulate reagent within the diluent prior to addition of the biological sample, the reagent and diluent are mixed by ultrasonic means. As disclosed in commonly owned U.S. patent application Ser. No. 575,924, filed Feb. 1, 1984, entitled "Clinical Analysis Systems and Methods", improved reliability and controllability of the analysis of the samples is achieved by again mixing the contents of the cuvette after addition of the sample by directing an air jet to an acute angle against the surface of the liquid in the cuvette. Particularly good mixing is obtained where the air jet is directed at the liquid surface adjacent its junction with the wall of the cuvette, the optimum point of contact of the air jet with the liquid surface being at the meniscus formed at the junction between the liquid surface and the wall of the cuvette.
A further advantageous feature of such an automated clinical analyzer is the use of microprocessor control, particularly for the dispensing and analysis station and the loading and transfer assembly for presenting to the analyzer containers having the samples to be tested.
A particular embodiment of the automated single track clinical analyzer according to aforesaid U.S. Pat. No. 4,528,159 is the subject of the Paramax Analytical System manufactured by American Dade, a division of American Hospital Supply Corporation, of Miami, Fla. "Paramax" is a registered trademark of American Hospital Supply Corporation. In this system, which is under microprocessor control, a cuvette belt is cut into sections, comprising one or several cuvettes, which are fed in turn past a reagent tablet dispenser, a diluent dispenser, an ultrasonic horn for mixing the reagent and diluent, a sample dispenser and eight photo-optical analyzer stations. During their passage through dispensing and analysis, the cuvettes are supported in a water bath kept at a constant temperature. After analysis, the cuvettes pass through a sealing station and into a disposal station.
Reagent tablets are dispensed from a rotary carousel and the biological liquids to be sampled are delivered in tubes to the sample dispenser one at a time by a carousel having priority access positions to allow immediate "stat" sample entry. Codes on the tubes identify the samples and a code-reader alerts the microprocessor to operate the analyzer in accordance with the coded information. A further reagent dispenser is arranged between two of the analyzer stations for producing further sample reaction to permit additional analysis.